The invention arose out of needs and concerns relating to open pit coal mining. Open pit mining commonly is performed using a combination of drilling and blasting techniques, and excavating machinery to remove material from the open pit. Excavating machinery is commonly used to break material away from a generally upright face of material for its subsequent removal from the mining pit. Such machinery can include a horizontally mounted, open cutter head having peripheral cutter elements such as teeth or buckets for breaking material from the face.
Presently accepted machinery has many drawbacks. For example, some excavating machinery is mounted on three or four track crawlers, requiring an inordinate amount of open pit area for maneuvering. Also, a number of excavators use bucket wheel cutting heads for breaking material from a face. These excavators rough cut a face of material, resulting in a significant loss of product from the face and requiring separate clean-up machines. Other excavators utilize open cutting heads also enabling the cuttings from the face to fall freely towards the floor of the pit for collection by separate equipment or a gathering arm and conveyor system. Such gathering systems require a large amount of maintenance. Additionally, material falling from the face generates an excessive amount of fumes and dust.
Accordingly, a need remains for improved excavating machinery which is capable of removing material from a tall face, minimizes dust generation, crushes material to a desirable level and transfers the material to separate removal equipment with a minimal degree of handling.